1. Field of Invention
This invention pertains to a portable cooling system for applying a controlled rate of cooling to a person or object. More particularly, this invention pertains to portable device that includes a cool water supply, a remote, tethered switching unit, and a thermal pad through which cool water is circulated.
2. Description of the Related Art
It is advantageous to selectively apply a cooling treatment to patients. Hypothermic treatment is useful for emergency treatment of injured persons, particularly those who have experienced head trauma. Cooling the brain immediately after a trauma event often can protect the brain and/or prevent or reduce injury to the brain. But, not only the brain benefits from cooling treatment. A common first aid for sports injuries is to apply ice or cooling to the injured area.
Cooling treatment is also useful for providing comfort. Many menopausal women have found relief from hot flashes by using cooling treatment to quickly lower their body temperature during the onset of a hot flash.
Physicians have used various devices and techniques to cool the human body, including pharmacological cooling and various types of mechanically induced cooling. Mechanically induced cooling approaches generally fall into one of three categories: conductive, convective, or evaporative. While different implementations have been tried, many are limited by lack of practicality, difficulty of use, ineffectiveness, and/or excessive power consumption.
Conductive cooling therapy, that is a cooling treatment in which the heat transfer mechanism is conduction as opposed to radiation or convection, is known and has been used. Ice packs, although primitive, provide quick localized cooling. A disadvantage of ice packs is that it is difficult to control the rate of cooling. It is also known to circulate a cooled fluid through a thermal pad wrapped around an extremity of a person. The fluid is cooled using various techniques, including using a refrigerant to cool the fluid.
A variety of conductive cooling therapy devices are known. U.S. Pat. No. 4,844,072, titled “Liquid-circulating thermal therapy system,” issued to French, et al., on Jul. 4, 1989, discloses a thermal therapy system 18 with a translucent reservoir 36 for indicating fluid level. A pump 96 mounted external to the reservoir 36 provides fluid to a thermal pad 22.
U.S. Pat. No. 5,336,249, issued to Mahawili on Aug. 9, 1994, titled “Portable body heating/cooling system and method of use,” discloses a pump 22 located inside a reservoir 14 and operated by an external battery 24. The inlet to the pump 22 is protected by a grill 32 “to prevent ice from entering and interfering with operation of the pump 22 and motor 30.” The supply and return tubes 18, 20, including their extensions 44, 48, have an internal diameter sized to minimize back pressure to the pump 22.
U.S. Pat. No. 5,476,489, issued to Koewler on Dec. 19, 1995, titled “Cold therapy system,” discloses an open top bag 11 filled with ice and water that is carried by a cooler 2. The bag 11 includes tubing flanges 14, 15 that allow connections to the bag 11 from outside the cooler 2. A housing 3 is attached to the outside of the cooler 2 and contains a positive displacement pump 4 and pump control means 5. The pump 4 is driven by a variable speed motor.
U.S. Pat. No. 5,486,207, issued to Mahawili on Jan. 23, 1996, titled “Thermal pad for portable body heating/cooling system and method of use,” discloses a portable reservoir 14 similar to that disclosed in U.S. Pat. No. 5,336,249. The supply and return tubes 18, 20, including their extensions 44, 48 have an internal diameter sized to minimize back pressure to the pump 22. The thermal pad 12 is formed from a single corrugated tube 50 following a serpentine path having a number of turns.
U.S. Pat. No. 5,647,051, issued to Neer on Jul. 8, 1997, titled “Cold therapy system with intermittent fluid pumping for temperature control,” discloses a cooler 2 being a reservoir for water and ice and a housing 3 mounted on the exterior of the cooler 2. The housing 3 includes a pump 4 and pump control means 5. The pump 4 is a single-speed, positive displacement pump. A cover 34 protects the pump control means 5 from condensation or leakage from the pump. The return tube 29 contains a liquid crystal temperature indicator 47. The pump control means 5 includes a circuit generating a pulse stream having two components. One component operates at a high frequency, such as 2 kHz, with a 25% on duty cycle. The second component operates at a very low frequency having a period of approximately 9 seconds. The second component has three duty cycles of 50%, 25%, and 11%. The two component pulse stream is applied to the pump motor 20 to control the flow from the pump. The return line 29 includes an orifice 29a. “The purpose of orifice 19a is to control the descent of pressure in pad 7 during motor-off times.”
U.S. Pat. No. 5,865,841, issued to Kolen, et al., on Feb. 2, 1999, titled “Cold therapy apparatus,” discloses a reservoir 19 and an external pump/heat exchanger 13. “The pump/heat exchanger 13, under microprocessor control, continuously displaces a precise amount of re-circulation water with water from the constant temperature reservoir to precisely maintain the temperature of the circulation water exiting the pump/heat exchanger 13.” “To ensure a uniform temperature distribution at the therapy site or sites, particularly when multiple bladders are used in series in post-bilateral surgery therapy, maximum flow rate and pressure through the circulation system is maintained.”
U.S. Pat. No. 5,948,012, issued to Mahaffey, et al., on Sep. 7, 1999, titled “Cold therapy device,” discloses a cold therapy unit 10 having two fluid loops. A first fluid loop includes a reservoir in an ice chest 14. The lid 16 to the ice chest 14 includes a manual control valve 17 and a first pump 18 that extends into the ice chest 14. The second fluid loop includes the electronic control unit 12 that includes an electronic valve 32, a second pump 34, a thermoelectric module 36, and a temperature probe 38. The first fluid loop charges the unit 10, after which the first fluid loop is isolated and the second fluid loop causes cool water to flow through a cold therapy pad 24. The second loop uses a thermoelectric module 36 to remove heat from the fluid loop. The first fluid loop is connected to the second fluid loop when the thermoelectric module 36 cannot maintain the cold temperature of the second fluid loop.
U.S. Pat. No. 6,551,348, issued to Blalock, et al., on Apr. 22, 2003, titled “Temperature controlled fluid therapy system,” discloses a reservoir 12, a continuously variable pump 17 submersed in the reservoir 12, a temperature controlled fluid blanket 18, and temperature sensors 20, 22. The two temperature sensors 20, 22 determine a control signal that controls the operation (the speed) of the pump 17. A high frequency (greater than 20 kHz) pulse output from the pulse width modulator 130 correlates to the temperature measured by the sensors 20, 22 to control the average power delivered to the submersible pump 17 via a power source 42.
Known prior art devices provide operator controls on the thermal therapy device. Oftentimes, it is desirable for a patient to control the thermal therapy device, either to start/stop the device or to control the temperature of the therapy pad. Many times the patient has limited mobility, hence the need for the therapy device. For these patients, a remote control unit to operate the thermal therapy device is advantageous.
Certain thermal pads that use a temperature controlled liquid benefit from maintaining a minimum pressure within the conduits of the pad. Such minimum pressure is useful to prevent the conduits in the thermal pad from being crushed or otherwise restricted, thereby enabling fluid flow through the conduits.
Known prior art devices use complicated configurations to control the temperature of the fluid directed to the thermal pad. The complicated configurations increase the complexity and the cost of thermal therapy devices. It is advantageous to use a passive system to control the temperature of the fluid flowing through the thermal pad.